Composite layered soft rock cylinder sample manufacturing device and preparation method

Abstract

The invention discloses a composite layered soft rock cylindrical sample manufacturing device and a preparation method, and relates to the field of geotechnical engineering test research, the composite layered soft rock cylindrical sample manufacturing device comprises a mold sleeve assembly, a clamp and a compaction hammer, the mold sleeve assembly is formed by coaxially butting an upper sleeve, a middle sleeve and a lower sleeve through a mortise and tenon joint structure to form a cylindrical test cavity, and the bottom of the mold sleeve assembly is supported by a leveler; the clamp comprises an upper clamp, a lower clamp and a fastening screw, the upper clamp presses the top end of the upper sleeve, the lower clamp is provided with a base for supporting the leveler, and the whole set of die is locked and fixed through the screw and a nut; the bottom end of the sliding rod is connected with the compaction block, and the top end of the sliding rod is provided with an anti-falling locking structure. According to the invention, the artificial sample with clear interlayer interface, accurate and controllable bedding inclination angle and stable mechanical property can be directly and quickly prepared without relying on core drilling, so that the problems of sampling disturbance, low efficiency and high cost in the prior art are effectively solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of geotechnical engineering test research, and in particular to a composite layered soft rock cylindrical sample preparation device and method. BACKGROUND

[0002] In the field of geotechnical engineering test research, indoor physical model test is an important means to study the mechanical properties and deformation and failure law of layered rock mass. Among them, uniaxial and triaxial compression test as a basic mechanical test method is widely used to obtain the strength and deformation parameters of rock mass. However, due to the heterogeneity, joint development and coring difficulty of the composite layered soft rock mass in nature, it is often difficult to directly obtain the undisturbed sample with regular size, clear bedding and uniform mechanical properties, which seriously restricts the reliability and repeatability of indoor test.

[0003] To overcome the above difficulties, three types of artificial preparation methods for layered rock samples have been developed in the prior art. The first type is to use adhesive to bond natural rock blocks into shape. Although this method is simple to operate, there is a significant difference between the strength of the artificial bonding surface and the strength of the natural rock bedding surface, which cannot truly reflect the mechanical behavior of the rock mass. The second type is to mix cement, gypsum and other cementitious materials with aggregates according to the proportion, then pour them layer by layer, and finally obtain cylindrical samples by coring. Although this method can adjust the material strength, the materials of each layer are easily intermingled during pouring, resulting in a blurred interface between the layers. Moreover, subsequent coring operations will cause mechanical disturbance to the sample and introduce micro-cracks. More importantly, when preparing samples with a specific bedding angle, inclined coring and secondary grinding of the sample end are required, which is a complex process with low efficiency and cannot meet the batch sample preparation requirements. The third type is to use 3D printing technology to accumulate layer by layer. This method has high precision and good repeatability, and can accurately control the characteristics of the structural surface. However, the equipment cost is high and the preparation period is long, which is also not suitable for large-scale sample preparation.

[0004] Therefore, how to develop a composite layered soft rock cylindrical sample preparation device and method, which can directly and quickly prepare artificial samples with clear interlayer interface, accurately controllable bedding angle and stable mechanical properties without relying on coring, to effectively solve the problems of sample disturbance, low efficiency and high cost existing in the prior art. SUMMARY

[0005] The purpose of the present application is to provide a composite layered soft rock cylindrical sample preparation device and method, which can directly and quickly prepare artificial samples with clear interlayer interface, accurately controllable bedding angle and stable mechanical properties without relying on coring, to effectively solve the problems of sample disturbance, low efficiency and high cost existing in the prior art.

[0006] To solve the above technical problems, the present application adopts the following technical solutions: The application discloses a composite layered soft rock cylindrical sample preparation device and method. The mold sleeve assembly comprises upper sleeves, at least one middle sleeve and a lower sleeve which are coaxially connected in sequence from top to bottom, the bottom of the lower sleeve is supported on a leveling device, the sleeves are butted through a concave-convex mortise and tenon structure, and the sleeves jointly enclose a cylindrical cavity for filling test materials. The clamp comprises an upper clamp, a lower clamp and a fastening screw, the lower clamp is provided with a base for supporting the leveling device, the upper clamp is arranged in a ring shape and is pressed on the top end of the upper sleeve, the bottom end of the fastening screw is connected to the lower clamp, the top end of the fastening screw is locked and fixed through a fixing hole on the periphery of the upper clamp after passing through a fixing nut, and the mold sleeve assembly composed of the upper sleeve, the middle sleeve and the lower sleeve is fastened and connected between the upper clamp and the lower clamp. The tamping hammer comprises a hammer block sliding rod, a hammer block and a tamping block, the hammer block is slidingly sleeved on the hammer block sliding rod, the tamping block is connected to the bottom end of the hammer block sliding rod, and the top end of the hammer block sliding rod is provided with a locking structure for limiting the hammer block from being separated.

[0007] Preferably, the locking structure comprises a locking ring and a locking nut which are installed on the top end of the hammer block sliding rod, the locking ring is sleeved on the hammer block sliding rod and located above the hammer block, and the locking nut is threadedly connected to the top end of the hammer block sliding rod and tightly fixes the locking ring.

[0008] Preferably, the top of the tamping block is provided with an internal threaded hole, the bottom end of the hammer block sliding rod is provided with an external thread, and the tamping block is threadedly connected to the bottom end of the hammer block sliding rod.

[0009] Preferably, the bottom of the tamping block is provided with a first inclined surface, the top of the leveling device is provided with a second inclined surface, and the first inclined surface and the second inclined surface are parallel to each other, so that the tamping block can be in full contact with the end surface of the sample placed on the leveling device during the compaction process.

[0010] Preferably, the connecting end surfaces between the upper sleeve, the middle sleeve and the lower sleeve are all inclined planes, and the inclined angles of all the sleeve end surfaces are consistent; when the upper sleeve, the middle sleeve and the lower sleeve are coaxially butted in sequence through the concave-convex mortise and tenon structure, the axis of the cylindrical cavity jointly enclosed by the sleeves forms an inclination angle with the horizontal plane.

[0011] Preferably, the bottom end of the fastening screw is connected to the base of the lower clamp in a hinged manner, so that the fastening screw can rotate relative to the lower clamp.

[0012] Preferably, the mold sleeve assembly, the clamp and the tamper are all made of high-strength aerospace aluminum alloy material.

[0013] A composite layered soft rock cylindrical sample preparation method, comprising the following steps: S1, raw material preparation: preparing paraffin and different colored quartz sand as raw materials; S2, independent heating: heating the quartz sand and paraffin separately in different heating containers, wherein the heating temperature of the quartz sand is controlled below 80℃, and the paraffin is heated to a completely molten liquid state; S3, mixing and stirring: pour the molten paraffin solution into the heated quartz sand, continuously stir to mix evenly, form a paraffin-quartz sand mixture, and maintain the temperature of the mixture in the range of 58℃-80℃ during the entire stirring process; S4, mold assembly: place the screed on the base of the lower clamp, then coaxially butt joint the lower sleeve, one or more middle sleeves and the upper sleeve on the screed through the mortise and tenon structure at the ends, then press fit the upper clamp on the top end of the upper sleeve, finally pass the fastening screw through the fixing hole of the upper clamp, and lock it with the fixing nut, so as to fasten and connect the entire mold sleeve assembly between the upper clamp and the lower clamp; S5, layering and filling: fill the hot paraffin-quartz sand mixture prepared in step S3 into the mold sleeve assembly assembled in step S4 in batches; then, vertically place the tamper in the top port of the upper sleeve, so that the tamper block contacts the surface of the mixture; then, lift the hammer block slide rod to drive the tamper block and the hammer block to rise to a certain height, then release the hammer block slide rod, so that the hammer block freely falls along the hammer block slide rod and impacts the tamper block at the bottom, thereby compacting and leveling the mixture in the sleeve through the impact force, and this tamping process can be repeated multiple times until the sample layer meets the preset compactness and flatness requirements; S6, layer-by-layer preparation: if the sample to be prepared is a multi-layer structure, after completing the filling of the current layer, loosen the fixing nut, add one or more middle sleeves above the filled sleeve, then re-execute the fastening operation of step S4 and the filling operation of step S5, and repeat until all design layers are prepared; S7, demolding and sampling: after the sample in the mold is completely cooled and solidified, sequentially disassemble the fixing nut, the upper clamp, the mold sleeve assembly and the screed, and finally obtain the formed composite layered soft rock cylindrical sample.

[0014] Preferably, during the stirring process of step S3, the temperature of the paraffin-quartz sand mixture is measured and monitored every two minutes.

[0015] Preferably, before assembling the mold sleeve assembly for the first time in step S4, a layer of rigid plastic cardboard is first attached to the inner wall surfaces of the upper sleeve, middle sleeve and lower sleeve respectively.

[0016] Compared with the prior art, the beneficial technical effects of the present invention are as follows: 1) By using a split combination design of upper sleeve, middle sleeve and lower sleeve, and by increasing or decreasing the number of middle sleeves to flexibly adjust the sample height, one device can meet the sample preparation needs of various experimental specifications, breaking through the limitations of traditional integral molds. 2) The mold sleeve components are joined by a mortise and tenon structure, combined with a rigid fastening frame consisting of an upper clamp, a lower clamp and a fastening screw, which effectively ensures the centering and overall stability of each sleeve during the compaction process, avoids interlayer misalignment and separation, and ensures the dimensional accuracy and structural integrity of the sample. 3) By pre-processing the end face of the sleeve into an inclined plane at a specific angle, and using a compaction block and leveler with a corresponding inclined plane at the bottom, cylindrical specimens with precise bedding angles can be directly formed, fundamentally avoiding the mechanical disturbance and secondary processing caused by traditional inclined core drilling sampling, and realizing the efficient and batch preparation of inclined specimens. 4) The fastening screw and the lower clamp are hinged, which can adapt to the clamping requirements of the mold components at different inclination angles and ensure the effective transmission of locking force; at the same time, the compaction block and the hammer block slide are connected by threads, which facilitates quick replacement according to the sample inclination angle requirements or wear conditions, improving the applicability and maintainability of the device. 5) The main components of the device are made of high-strength aerospace aluminum alloy, which not only ensures the structural strength and dimensional stability of the mold under repeated impact loads, but also utilizes its good machinability to achieve high-precision tilting and smooth inner wall, which is conducive to demolding and ensures the surface quality of the sample. Attached Figure Description

[0017] The present invention will be further described below with reference to the accompanying drawings.

[0018] Figure 1 This is a schematic diagram of the connection structure between the mold sleeve assembly and the clamp in a composite layered soft rock cylindrical sample preparation device of the present invention. Figure 2 In this invention Figure 1 The main view; Figure 3 In this invention Figure 1 Top view; Figure 4 This is a schematic diagram of the impact hammer in this invention; Figure 5 In this invention Figure 4 Side view; Figure 6 is a top view of the upper clamp in the application; Figure 7 is a side view of the upper clamp in the application; Figure 8 is a top view of the lower clamp in the application; Figure 9 is a side view of the lower clamp in the application; Figure 10 is a front view of the screed in the application.

[0019] Mark explanation: 1, upper clamp; 2, lower clamp; 3, fixed nut; 4, fastening screw; 5, locking nut; 6, locking ring; 7, hammer block slide rod; 8, hammer block; 9, tamping block; 10, upper sleeve; 11, middle sleeve; 12, lower sleeve; 13, screed; 14, fixed hole position. DETAILED DESCRIPTION

[0020] In order to make the technical problems to be solved by the application, the technical scheme and the beneficial effects more clear and obvious, the application will be further described in detail below in combination with the drawings and examples. It should be understood that the specific examples described herein are only used to explain the application and not to limit the application.

[0021] As shown in Figures 1-10 A composite layered soft rock cylindrical specimen preparation device, comprising a mold sleeve assembly, a clamp and a tamping hammer; The mold sleeve assembly comprises an upper sleeve 10, at least one middle sleeve 11 and a lower sleeve 12 connected coaxially in sequence from top to bottom, the bottom of the lower sleeve 12 is supported on a screed 13, the sleeves are butted through a concave-convex mortise and tenon structure, and together enclose a cylindrical cavity for filling test materials; The clamp comprises an upper clamp 1, a lower clamp 2 and a fastening screw 4, the lower clamp 2 is provided with a base for supporting the screed 13, the upper clamp 1 is arranged in a ring shape and is pressed on the top end of the upper sleeve 10, the bottom end of the fastening screw 4 is connected to the lower clamp 2, and the top end of the fastening screw 4 is locked and fixed through a fixed nut 3 after passing through the fixed hole position 14 provided on the periphery of the upper clamp 1, so that the mold sleeve assembly composed of the upper sleeve 10, the middle sleeve 11 and the lower sleeve 12 is fastened and connected between the upper clamp 1 and the lower clamp 2; The tamping hammer comprises a hammer block slide rod 7, a hammer block 8 and a tamping block 9, the hammer block 8 is slidably sleeved on the hammer block slide rod 7, the tamping block 9 is connected to the bottom end of the hammer block slide rod 7, and the top end of the hammer block slide rod 7 is provided with a locking structure for limiting the hammer block 8 from being separated.

[0022] Specifically, the mold sleeve assembly adopts a split combination design of the upper sleeve 10, the middle sleeve 11 and the lower sleeve 12, and the total height of the prepared sample is flexibly controlled by increasing or decreasing the number of the middle sleeve 11. This modular structure solves the limitation of the traditional integral mold that can only prepare samples of a fixed height, so that one set of device can meet the needs of various experimental specifications. At the same time, the rigid frame composed of the upper clamp 1, the lower clamp 2 and the fastening screw 4 provides overall constraint and fastening for the split sleeve assembly, effectively eliminating the possible movement or separation of each sleeve under repeated impact of the tamping hammer, thereby ensuring the dimensional accuracy and integrity of the sample forming.

[0023] Specifically, the locking structure includes a locking ring 6 mounted at the top end of the hammer block slide rod 7 and a locking nut 5. The locking ring 6 is sleeved on the hammer block slide rod 7 and located above the hammer block 8, and the locking nut 5 is threadedly connected at the top end of the hammer block slide rod 7 and tightly fixes the locking ring 6.

[0024] Specifically, the top of the tamping block 9 is provided with an internal threaded hole, and the bottom end of the hammer block slide rod 7 is provided with an external thread. The tamping block 9 is threadedly connected at the bottom end of the hammer block slide rod 7.

[0025] Specifically, in actual application, in order to prepare samples with different bedding dip angles, tamping blocks 9 with corresponding inclined angles at the bottom are required to ensure that the compaction surface completely matches the end surface of the sample. The tamping block 9 and the hammer block slide rod 7 are threadedly connected, so that the operator can quickly and accurately replace the matching tamping block 9 according to the experimental scheme, which not only expands the application range of a single set of device, but also facilitates the replacement of the working surface of the tamping block 9 after wear, thereby improving the applicability and maintenance convenience of the device.

[0026] Specifically, the bottom of the tamping block 9 is provided with a first inclined surface, and the top of the screed 13 is provided with a second inclined surface. The first inclined surface and the second inclined surface are parallel to each other, so that the tamping block 9 can maintain full contact with the end surface of the sample placed on the screed 13 during the compaction process.

[0027] Specifically, the connecting end surfaces between the upper sleeve 10, the middle sleeve 11 and the lower sleeve 12 are all inclined planes, and the inclined angles of all the sleeve end surfaces are consistent. When the upper sleeve 10, the middle sleeve 11 and the lower sleeve 12 are coaxially butted in sequence through the convex-concave mortise and tenon structure, the axis of the cylindrical cavity enclosed by them forms an inclination with the horizontal plane.

[0028] Specifically, the upper sleeve 10, the middle sleeve 11 and the lower sleeve 12 all have inclined end faces with the same angle, and when they are coaxially connected through the mortise and tenon structure, the inner cavities naturally form a cylindrical space with a fixed angle with the horizontal plane. This design directly defines the sample bedding dip angle in the physical structure, and from the root, it abandons the cumbersome process of pouring the block first and then inclining the core in the traditional method. Not only does it avoid mechanical disturbance and damage to the internal structure of the sample during the drilling process, but it also ensures the original mechanical properties of the sample material. At the same time, it also realizes the one-time forming and batch preparation of the layered sample with consistent dip angle, greatly improving the efficiency of the experiment and the reliability of the data.

[0029] Specifically, the top end of the upper sleeve 10 and the bottom end of the lower sleeve 12 are both set as horizontal end faces.

[0030] Specifically, the bottom end of the fastening screw 4 is connected to the base of the lower clamp 2 through a hinged manner, so that the fastening screw 4 can rotate relative to the lower clamp 2.

[0031] Specifically, the bottom end of the fastening screw 4 is connected to the base of the lower clamp 2 through a hinged manner, which allows the fastening screw 4 to have a certain degree of freedom. The core advantage is that it can adapt to different dip angle mold sleeve assemblies. When assembling the sleeve with an inclined end face, the plane of the upper clamp 1 is no longer parallel to the base of the lower clamp 2, and the hinged design allows the fastening screw 4 to angle during locking, ensuring that the locking force acts vertically on the upper clamp 1, avoiding the installation difficulty or stress concentration problem caused by rigid connection, and ensuring the clamping stability of samples with different dip angles during preparation.

[0032] Specifically, the mold sleeve assembly, the clamp and the tamping hammer are all made of high-strength aerospace aluminum alloy material.

[0033] Specifically, the mold sleeve assembly, the clamp and the tamping hammer are all made of high-strength aerospace aluminum alloy material. On the one hand, the high strength and hardness of aerospace aluminum alloy can effectively resist the high stress caused by repeated impact of the tamping hammer, preventing plastic deformation or damage of the mold, thereby ensuring the long-term accuracy and stability of the sample size. On the other hand, this material has good machining performance, which can realize high-precision inclination angle machining of the sleeve end face and smooth inner wall surface, which is crucial for ensuring perfect interlayer fit, reducing demolding resistance and obtaining regular sample shape.

[0034] A composite layered soft rock cylindrical sample preparation method, comprising the following steps: S1, raw material preparation: prepare paraffin and different colored quartz sand as raw materials. The paraffin used in this embodiment is 58# full refined paraffin, with a melting point of 58℃ and a boiling point of about 80℃. S2, independent heating: quartz sand and paraffin are placed in different heating containers for heating, wherein the heating temperature of quartz sand is controlled below 80℃, and paraffin is heated to a completely molten liquid state; S3, mixing and stirring: pour the molten paraffin solution into the heated quartz sand, continuously stir to mix uniformly, form a paraffin-quartz sand mixture, and maintain the temperature of the mixture in the range of 58℃-80℃ during the whole stirring process; S4, mold assembly: place the screed 13 on the base of the lower clamp 2, then coaxially butt joint the lower sleeve 12, one or more middle sleeves 11 and the upper sleeve 10 on the screed 13 in sequence through the mortise and tenon structure at the ends of the sleeves, then press fit the upper clamp 1 on the top end of the upper sleeve 10, finally pass the fastening screw 4 through the fixed hole 14 of the upper clamp 1, and lock it with the fixed nut 3, so as to fasten and connect the whole mold sleeve assembly between the upper clamp 1 and the lower clamp 2; S5, layer filling: fill the hot paraffin-quartz sand mixture prepared in step S3 into the mold sleeve assembly assembled in step S4 in batches; then, vertically place the tamper hammer into the top port of the upper sleeve 10, so that the tamper block 9 contacts the surface of the mixture; then, lift the hammer block slide rod 7 to drive the tamper block 9 and the hammer block 8 to rise to a certain height, then release the hammer block slide rod 7, so that the hammer block 8 freely falls along the hammer block slide rod 7 and impacts the tamper block 9 at the bottom, so as to compact and flatten the mixture in the sleeve through the impact force, and the compaction process can be repeated for multiple times until the sample in the layer reaches the preset compactness and flatness requirements; S6, layer-by-layer preparation: if the sample to be prepared is a multi-layer structure, after the filling of the current layer is completed, loosen the fixed nut 3, add one or more middle sleeves 11 above the filled sleeve, then re-perform the fastening operation of step S4 and the filling operation of step S5, and repeat the above steps until all the designed layers are prepared; S7, demolding and sampling: after the sample in the mold is completely cooled and solidified, sequentially disassemble the fixed nut 3, the upper clamp 1, the mold sleeve assembly and the screed 13, and finally obtain the formed composite layered soft rock cylindrical sample.

[0035] Specifically, the independent temperature control heating of the quartz sand and the paraffin in step S2 avoids the over-heating sublimation of the paraffin and the inaccurate actual proportioning, which is the premise of ensuring the controllable strength parameters of the sample, and the gravity impact compaction in step S5 instead of static compaction can make the arrangement of the material particles more compact and the internal structure closer to the natural rock mass compacted by geological action, and meanwhile, the layer-by-layer preparation process in step S6 can accurately reconstruct the alternating bedding of the soft and hard rocks with different strengths and colors in one sample by controlling the paraffin content, i.e., the binder content and the color of each layer of material, thereby providing a highly similar physical model for the indoor mechanical test.

[0036] Specifically, the layer-by-layer preparation operation in step S6 needs to be completed in a short time, so as to fully utilize the residual heat of the last batch of materials. When the new middle sleeve 11 is filled with the new hot mixture, the heat can be transferred to the upper surface of the formed layer, so that the surface paraffin is slightly softened and melted, thereby realizing the firm 'thermal bonding' with the new material. This process effectively simulates the original bonding state between the layers in the natural rock mass, and avoids the problem of obvious weakly bonded interface of the artificial sample.

[0037] Specifically, the temperature of the paraffin-quartz sand mixture is measured and monitored every two minutes during the stirring process in step S3.

[0038] Specifically, the mixture temperature is monitored every two minutes during the stirring process in step S3, and the purpose is to accurately control the physical state of the mixture: when the temperature is lower than 58℃, the paraffin will start to solidify, resulting in uneven mixing with the quartz sand and weakening the bonding effect; and when the temperature is higher than 80℃, the paraffin will be severely gasified, causing the loss of the binder and directly changing the designed proportioning and strength of the material. The present application can ensure that the mixture is always in a molten and stable viscous flow state by implementing this high-frequency temperature monitoring, thereby ensuring that each batch of prepared samples has high repeatability and consistent mechanical properties.

[0039] Specifically, before the first assembly of the mold sleeve assembly in step S4, a layer of hard plastic card paper is placed on the inner wall surface of the upper sleeve 10, the middle sleeve 11 and the lower sleeve 12, respectively.

[0040] Specifically, before assembling the mold in step S4, a layer of hard plastic card paper is pasted on the inner wall of each sleeve, which mainly functions to achieve non-destructive demolding. Paraffin-based materials will produce strong adhesion with the inner wall of the metal mold during the cooling and solidification process. If direct demolding is performed, it is extremely easy to cause tearing or scratching on the surface of the soft rock sample with low strength. The surface of the hard plastic card paper is smooth and flexible, which can effectively prevent the direct bonding of paraffin and metal mold on one hand, and on the other hand, it can slightly deform with the sample when the mold is disassembled, so as to separate from the sample with extremely small friction, ensuring that the formed cylindrical sample, especially the sample with multi-layer composite structure, can be taken out completely and non-destructively, maintaining the structural integrity for subsequent experimental use.

[0041] It should be noted that, in this document, the terms such as first and second are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "comprise", "include" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not explicitly listed or inherent to such a process, method, article or device.

[0042] The above-described embodiments are only to describe the preferred modes of the present application, and not to limit the scope of the present application. Without departing from the design spirit of the present application, various modifications and improvements to the technical solutions of the present application made by those skilled in the art shall fall within the protection scope determined by the claims of the present application.

Claims

1. A device for preparing composite layered soft rock cylindrical samples, characterized in that: Includes mold sleeve assembly, clamps and compaction hammer; The mold sleeve assembly includes an upper sleeve (10), at least one middle sleeve (11) and a lower sleeve (12) connected coaxially from top to bottom. The bottom of the lower sleeve (12) is supported on the leveler (13). The sleeves are connected by a tenon and mortise structure to form a cylindrical cavity for filling the test material. The clamp includes an upper clamp (1), a lower clamp (2) and a fastening screw (4). The lower clamp (2) is provided with a base for supporting the leveler (13). The upper clamp (1) is annular and pressed against the top of the upper sleeve (10). The bottom end of the fastening screw (4) is connected to the lower clamp (2). The top end of the fastening screw (4) passes through the fixing hole (14) provided around the upper clamp (1) and is locked by the fixing nut (3). Thus, the mold sleeve assembly composed of the upper sleeve (10), the middle sleeve (11) and the lower sleeve (12) is fastened between the upper clamp (1) and the lower clamp (2). The compaction hammer includes a hammer block slide rod (7), a hammer block (8) and a compaction block (9). The hammer block (8) is slidably sleeved on the hammer block slide rod (7). The compaction block (9) is connected to the bottom end of the hammer block slide rod (7). The top end of the hammer block slide rod (7) is provided with a locking structure to restrict the hammer block (8) from disengaging.

2. The composite layered soft rock cylindrical sample preparation device according to claim 1, characterized in that: The locking structure includes a locking ring (6) and a locking nut (5) installed on the top of the hammer block slide (7). The locking ring (6) is sleeved on the hammer block slide (7) and located above the hammer block (8). The locking nut (5) is threaded to the top of the hammer block slide (7) and presses the locking ring (6) tightly.

3. The composite layered soft rock cylindrical sample preparation device according to claim 2, characterized in that: The top of the compaction block (9) is provided with an internal threaded hole, and the bottom end of the hammer block slide rod (7) is provided with an external thread. The compaction block (9) is threadedly connected to the bottom end of the hammer block slide rod (7).

4. The composite layered soft rock cylindrical sample preparation device according to claim 3, characterized in that: The bottom of the compaction block (9) is set as a first inclined surface, and the top of the leveler (13) is set as a second inclined surface. The first inclined surface and the second inclined surface are parallel to each other, so that the compaction block (9) can maintain full contact with the sample end face placed on the leveler (13) during the compaction process.

5. The composite layered soft rock cylindrical sample preparation device according to claim 4, characterized in that: The connecting end faces between the upper sleeve (10), the middle sleeve (11) and the lower sleeve (12) are all inclined planes, and the inclination angle of all sleeve end faces is the same; when the upper sleeve (10), the middle sleeve (11) and the lower sleeve (12) are connected coaxially in sequence through the mortise and tenon structure, the axis of the cylindrical cavity formed by them together forms an angle with the horizontal plane.

6. The composite layered soft rock cylindrical sample preparation device according to claim 5, characterized in that: The bottom end of the fastening screw (4) is connected to the base of the lower clamp (2) by a hinge, so that the fastening screw (4) can rotate relative to the lower clamp (2).

7. The composite layered soft rock cylindrical sample preparation device according to claim 5, characterized in that: The mold sleeve assembly, clamp, and compaction hammer are all made of high-strength aerospace aluminum alloy.

8. A method for preparing a composite layered soft rock cylindrical sample, characterized in that: A composite layered soft rock cylindrical sample preparation device according to any one of claims 1 to 7 includes the following steps: S1, Raw material preparation: Prepare paraffin wax and quartz sand of different colors as raw materials; S2, Independent Heating: Quartz sand and paraffin wax are placed in separate heating containers for heating. The heating temperature of quartz sand is controlled below 80℃, while paraffin wax is heated to a completely molten liquid state. S3, Mixing and stirring: Pour the molten paraffin solution into the heated quartz sand and stir continuously to mix it evenly, forming a paraffin-quartz sand mixture. During the entire stirring process, maintain the temperature of the mixture within the range of 58℃ to 80℃. S4, Mold assembly: Place the leveler (13) on the base of the lower clamp (2), then sequentially connect the lower sleeve (12), one or more middle sleeves (11) and the upper sleeve (10) to the leveler (13) through the mortise and tenon structure at their ends, then press the upper clamp (1) onto the top of the upper sleeve (10), and finally pass the fastening screw (4) through the fixing hole (14) of the upper clamp (1) and lock it with the fixing nut (3), thereby fastening the entire mold sleeve assembly between the upper clamp (1) and the lower clamp (2); S5, Layered compaction: The hot paraffin-quartz sand mixture prepared in step S3 is filled into the mold sleeve assembly assembled in step S4 in batches; then, the compaction hammer is vertically placed into the top port of the upper sleeve (10) so that the compaction block (9) contacts the surface of the mixture; then, the compaction block (9) and the hammer block (8) are raised together to a certain height by lifting the hammer block slide rod (7), and then the hammer block slide rod (7) is released so that the hammer block (8) falls freely along the hammer block slide rod (7) and impacts the compaction block (9) at its bottom. The mixture in the sleeve is compacted and leveled by the impact force, and this compaction process can be repeated many times until the sample layer reaches the preset density and flatness requirements; S6, layer-by-layer preparation: If the sample to be prepared is a multi-layer structure, after the current layer is filled, loosen the fixing nut (3), add one or more middle sleeves (11) above the filled sleeve, and then re-execute the tightening operation of step S4 and the filling operation of step S5. Repeat this process until all designed layers are prepared. S7, Demolding and Sampling: After the sample in the mold has completely cooled and solidified, the fixing nut (3), upper clamp (1), mold sleeve assembly and leveler (13) are disassembled in sequence to finally obtain the formed composite layered soft rock cylinder sample.

9. The method for preparing a composite layered soft rock cylindrical sample according to claim 8, characterized in that: During the stirring process in step S3, the temperature of the paraffin-quartz sand mixture is measured and monitored every two minutes.

10. The method for preparing a composite layered soft rock cylindrical sample according to claim 8, characterized in that: Before assembling the mold sleeve assembly for the first time in step S4, a layer of rigid plastic card is first attached to the inner wall surfaces of the upper sleeve (10), middle sleeve (11) and lower sleeve (12).

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